Estuaries are coastal regions where freshwater from rivers and streams meets and mixes with saltwater from the ocean. These areas are characterized by tidal influences and are often partially enclosed by land, leading to unique ecological conditions. Estuaries can take the form of lagoons, bays, or river mouths. The mixing of saltwater and freshwater creates a specific environment that supports diverse habitats and a wide range of plant and animal species, making estuaries one of the most productive ecosystems in the world.

The term "fjords" refers to long, deep, narrow inlets of the sea that are usually surrounded by steep cliffs or mountains. They are formed by the glacial erosion of valleys, where glaciers retreat, leaving behind a U-shaped valley that fills with seawater when the sea level rises. Fjords are characterized by their dramatic landscapes, often featuring steep terrains, waterfalls, and rich marine ecosystems.

An archipelago is a group or chain of islands clustered together in a body of water. These islands can vary in size, geological origin, and ecological characteristics. Archipelagos can be found in oceans, seas, and even large lakes. They can consist of a few small islands or be made up of hundreds of islands.

Sea caves are natural formations created by the erosive action of ocean waves on coastal rock. These caves typically develop in cliffed shorelines where the relentless pounding of waves can carve out voids in the rock over time. They can vary widely in size and shape, and are often characterized by their unique geological features. Sea caves can be found in various types of rock, including limestone, sandstone, and basalt, and they may possess fascinating attributes like arches, blowholes, and interesting mineral formations.

"Seas" can refer to a few different concepts depending on the context: 1. **Geographical Term**: In a geographical context, "seas" are large bodies of saltwater, typically smaller than oceans and partially enclosed by land. Examples include the Mediterranean Sea, the Red Sea, and the Caribbean Sea.

In geographical terms, a "sound" is a large sea or ocean inlet. It can also refer to a narrow sea or ocean channel between two landmasses. Sounds are typically larger than fjords and are often less sheltered than bays. They are formed through various geological processes, including erosion and glacial activity. Sounds can also serve important ecological and economic functions, acting as habitats for marine life and providing navigation routes for shipping and fishing.

Landforms by the sea or ocean refer to various natural features that are formed along coastlines and in marine environments. These landforms can be shaped by various geological processes, including erosion, sediment deposition, and tectonic activity. Here are some common types of coastal landforms: 1. **Beaches**: Sandy or pebbly areas along the shoreline where wave action deposits sediment.

River deltas are landforms that develop at the mouth of a river where it meets a body of water, such as a lake, sea, or ocean. They are created by the accumulation of sediment that is carried downstream by the river's flow and deposited when the river's velocity decreases as it enters a larger body of water. This sediment builds up over time, forming a triangular or fan-shaped area of land.

The term "Bay" can refer to several different things depending on the context. Here are some common meanings: 1. **Geographical Feature**: A bay is a body of water partially enclosed by land, typically smaller than a gulf. Bays can be found along coastlines and are often characterized by calm waters. 2. **Bay in Architecture**: In architecture, a bay refers to a division of a building or a space within it, typically marked by supports like columns or walls.

A raised coral atoll is a type of geological formation that occurs when a coral reef, typically an atoll, is uplifted above sea level. Atolls are ring-shaped coral reefs that encircle a lagoon, often formed around volcanic islands. Over time, geological processes such as tectonic uplift, changes in sea level, or volcanic activity can raise these coral structures above the ocean surface. Raised coral atolls showcase unique ecosystem characteristics and provide important insights into past sea-level changes and geological history.

A spit is a geographical landform that is a type of shoreline feature, typically formed by the accumulation of sand and sediment. It extends from the coast into a body of water, such as a sea or lake, and is usually shaped like a long, narrow stretch of land. Spits are formed through the process of longshore drift, which involves the lateral movement of sediments along the coast due to wave action and current flow.

Undersea banks, also known as underwater banks or sea mounts, refer to underwater topographical features that rise from the ocean floor but do not reach the surface of the water. These features can take the form of banks, reefs, or hills and are typically formed through geological processes such as volcanic activity or sedimentation. In a broader context, the term "undersea banks" can also refer to areas of the ocean that have significant biological, geological, or chemical resources.

In geology, a "blowhole" refers to a geological feature typically found along coastlines, formed when waves force water into fissures or cracks in rock formations, often leading to the creation of a vertical shaft or tunnel through which water is expelled. When the incoming waves hit the rocks, they can cause a sudden surge of water to shoot upwards through these openings, creating a fountain-like effect.

In geology, "stacks" refer to geological formations that are typically characterized by vertical columns of rock that rise abruptly from the surrounding landscape, often found near coastlines. These structures are formed through processes of erosion, where softer rock layers are worn away by waves and weather, leaving behind more resistant rock that stands taller than the surrounding area. Stacks are usually associated with sea cliffs and are often remnants of larger rock formations that have been eroded over time.

In the context of mathematics, particularly in the study of Lie groups and Lie algebras, a **Cartan pair** refers to a specific structure that arises in the theory of semisimple Lie algebras.

Chromatic homotopy theory is a branch of algebraic topology that studies stable homotopy groups of spheres and related phenomena through the lens of chromatic filtration. It originated from attempts to better understand the relationship between stable homotopy theory and complex-oriented cohomology theories, particularly in the context of the stable homotopy category.

Cohomology is a fundamental concept in algebraic topology and other fields of mathematics that studies the properties of spaces through algebraic invariants. It provides a way to associate a sequence of abelian groups or vector spaces to a topological space, which can help in understanding its structure and features.

An anchialine system is a coastal ecosystem characterized by a body of water that is partially or wholly enclosed, usually by land, and has a connection to the ocean but with limited or no horizontal exchange. These systems are typically found in limestone or volcanic areas and contain both fresh and saltwater, often resulting from the mixing of groundwater with seawater.

Arm refers to a geographic term that designates a section of land or water that extends from a larger body. It can be used in various contexts, such as describing a river's tributary or a part of a bay or inlet. For example, the "Arm" might refer to a narrow part of a body of water that extends into the land, adding complexity to the coastline or landscape.

An atoll is a ring-shaped coral reef, island, or series of islets that encircle a lagoon either partially or completely. Atolls are typically formed from the growth of coral reefs around the rim of submerged volcanic islands. Over time, as the volcanic island erodes and sinks, the coral continues to grow upward, maintaining its structure and forming an atoll.